Lung cancer is the most common cause of cancer death worldwide. About 90% of all lung cancers are directly attributable to smoking. Despite considerable efforts in reducing the prevalence of tobacco use in the U.S., over 45 million adult Americans are still smokers. Former smokers are also at a high risk of lung cancer. One promising alternative approach to reduce lung cancer mortality is the use of chemopreventive agents. Currently, there is not any effective cancer chemopreventive agent for human use. Our long-term goal is to develop effective lung cancer chemopreventive agents which can inhibit lung cancer in current and former smokers. We propose that indole-3-carbinol (I3C), a constituent of Brassica vegetables, inhibits 4- (methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK)-induced lung tumorigenesis in A/J mice and modulates carcinogen-induced alterations in protein levels. NNK is highly implicated in tobacco-induced lung cancer in smokers. Our hypothesis is based on (1) Epidemiologic studies which indicate an inverse association between high consumption of Brassica vegetables and the incidence of lung cancer; (2) The high concentration of indole glucosinolates, the parent compounds for I3C, in Brassica vegetables; (3) Cancer preventive activity of I3C in in vitro and in vivo lung cancer models; and (4) modulation by I3C of tumorigenesis-related genes/proteins. Our aims in this proposal are: (1) Test the chemopreventive efficacy of I3C against NNK-induced lung tumorigenesis in A/J mice. Mice will be treated with NNK and given I3C at different temporal sequences, or for different durations of time, lungs harvested and incidence and multiplicity of macroscopic and microscopic tumors determined. (2) Identify differentially expressed proteins in type II pneumocytes, the cells from which lung adenoma arise, of NNK-, NNK plus I3C, or I3C-treated A/J mice. For this, we will use relative and absolute quantitation (iTRAQ) proteomics technology and antibody-based protein microarray. (3) Identify, using antibody-based protein microarray approach, differential proteomic patterns in the serum and bronchoalveolar lavage fluid (BALF) of mice treated with NNK, I3C, or NNK and I3C and assess functional consequences of alterations in protein levels. Overall, the results of this project will provide a solid platform for clinical trials of I3C as a chemopreventive agent against lung cancer.